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Fri, 20 Nov 2020 07:55:16 -0800 (PST) Date: Fri, 20 Nov 2020 07:55:14 -0800 From: Minchan Kim To: Peter Zijlstra Subject: Re: [PATCH 4/6] mm: proc: Invalidate TLB after clearing soft-dirty page state Message-ID: <20201120155514.GA3377168@google.com> References: <20201120143557.6715-1-will@kernel.org> <20201120143557.6715-5-will@kernel.org> <20201120150023.GH3040@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20201120150023.GH3040@hirez.programming.kicks-ass.net> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201120_105521_558900_EE3F4EBB X-CRM114-Status: GOOD ( 19.79 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Yu Zhao , Will Deacon , Anshuman Khandual , Linus Torvalds , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Catalin Marinas , kernel-team@android.com, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Nov 20, 2020 at 04:00:23PM +0100, Peter Zijlstra wrote: > On Fri, Nov 20, 2020 at 02:35:55PM +0000, Will Deacon wrote: > > Since commit 0758cd830494 ("asm-generic/tlb: avoid potential double flush"), > > TLB invalidation is elided in tlb_finish_mmu() if no entries were batched > > via the tlb_remove_*() functions. Consequently, the page-table modifications > > performed by clear_refs_write() in response to a write to > > /proc//clear_refs do not perform TLB invalidation. Although this is > > fine when simply aging the ptes, in the case of clearing the "soft-dirty" > > state we can end up with entries where pte_write() is false, yet a > > writable mapping remains in the TLB. > > > > Fix this by calling tlb_remove_tlb_entry() for each entry being > > write-protected when cleating soft-dirty. > > > > > @@ -1053,6 +1054,7 @@ static inline void clear_soft_dirty(struct vm_area_struct *vma, > > ptent = pte_wrprotect(old_pte); > > ptent = pte_clear_soft_dirty(ptent); > > ptep_modify_prot_commit(vma, addr, pte, old_pte, ptent); > > + tlb_remove_tlb_entry(tlb, pte, addr); > > } else if (is_swap_pte(ptent)) { > > ptent = pte_swp_clear_soft_dirty(ptent); > > set_pte_at(vma->vm_mm, addr, pte, ptent); > > Oh! > > Yesterday when you had me look at this code; I figured the sane thing > to do was to make it look more like mprotect(). > > Why did you chose to make it work with mmu_gather instead? I'll grant > you that it's probably the smaller patch, but I still think it's weird > to use mmu_gather here. I agree. The reason why clear_refs_write used the gather API was [1] and seems like to overkill to me. We could just do like [inc|dec]_tlb_flush_pending with flush_tlb_mm at right before dec_tlb_flush_pending instead of gather. thought? [1] b3a81d0841a95, mm: fix KSM data corruption _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel